You're right as rain. There are MILLIONS of us who are ready for a THIRD PARTY and right NOW.
But, their very success split the Tories. The result was a veritable Liberal hegemony from 1993 to 2006, when Stephen Harper became Prime Minister. For his first two terms, he had to all but drop the socon planks because he only had a minority government [i.e., a plurality of seats in Parliament but not a majority.]
The third, conservative party idea might well be viable now because of disillusionment/disgust at Romney and the GOP Establishment. But, the above recounting - much more recent than your narrative about the decline of the Whigs - shows you what you'll likely be in for. If you think you can abide the risk - Dems enjoying a virtual hegemony in Congress and the Presidency for about a decade - then by all means go for it. Just keep in mind that you'll attract more than your share of doomsayers. They won't mind the idea of the Dems having a virtual hegemony because they like the idea of a collapse being blamed squarely on the Dems. They might well be your happy warriors in the third party.
But that means you'll have trouble grafting the old Reaganism onto the party. Reaganauts, being professional optimists, won't mix very well with the doomsayers.
Just to let you know: I'm posting this reply to inform, not to dissuade. I lived through something similar in Canada, and want any third partiers to get an idea of what they're in for if they succeed in representing those millions.